Most common ink jet drop ejectors are thermal or acoustic. Thermal ink jet (TIJ) technologies are based upon rapid nucleation which takes place within a channel containing a water based ink. Such a technology is very limited in its ability for "on demand" drop size modulation due to adding complexity and cost through the addition of multiple channel heaters of various sizes. The thermal ink jet technology is also limited in life characteristics due primarily to the intense heat that is generated and the subsequent thermal stressing and adverse reaction with inks. Additionally, thermal ejectors can be fairly inefficient and, as stated previously, can also generate a lot of heat.
Acoustic ejectors either displace a volume or propagate an acoustic pressure to generate a fluid drop. One of the most common of this type of technology is piezo based. Piezo technologies are theoretically capable of "on demand" drop size modulation and, because of the piezoelectric nature of their actuation, well designed applications have very long life characteristics. However, piezo based technologies are disadvantaged due to the high cost of processing piezo materials and the resulting size of an ink jet array (number of nozzles). Another type of acoustic ejector is Acoustic Ink Jet (AIP). Again, AIP suffers from the difficulty of making small structures such as 600 DPI, and also is fairly inefficient and costly.
Some electrostatically actuated ink jet technologies are based upon deformation of a membrane in a totally enclosed structure via electrostatic forces. Because of the totally enclosed, hence highly constrained structure, very large ejection mechanisms must be considered to compensate for the very small deformation of the membrane. This leads to very small drop sizes, very large ejection mechanisms, very large applied voltages and/or very high costs.